In the majority of current avionic systems, the detection and confirmation of a fault are accomplished by following a sequential treatment. A first analysis is performed with an instantaneous detection technique and then a confirmation delay is used before confirmation of the existence of the fault and the treatment thereof by a maintenance system.
As illustrated in FIG. 1, the current avionic fault detection systems 105 are based on the ARINC 624 standard (ARINC being the acronym for Aeronautical Radio, Incorporated, a registered trademark), in which a software agent 110 within the systems (known in English as “Built-In Test Equipment”, or BITE) has the task of collecting raw detection information items arriving from the operational part 115 for surveillance of the system. Agent 110 consolidates these information items in time and analyzes them in order to diagnose whether an equipment item is faulty in the system. In the case of detection of a fault, agent 110 sends a diagnostic message to a centralized maintenance system 120, or CMS (acronym for “Centralized Maintenance System”). The CMS correlates the messages from the different systems of the airplane. The function of consolidation block 111 of agent 110 most often consists in adding an additional confirmation delay in order to increase the confidence in the persistence of the fault before transmitting a fault diagnosis to CMS 120. Report (“reporting”) block 112 effects emission of the fault diagnosis message. Memory block 113 stores the raw data with which a fault has been detected as well as the contents of the fault diagnosis messages.
FIG. 2 illustrates, in a timing diagram, the principle of consolidation effected by block 111. At an instant 205, an event capable of representing a fault is received by operational part 115. If the signal representative of this event does not continue for a delay 210, operational part 115 does not transmit a message to agent 110, as illustrated in the first line of FIG. 2. If, on the contrary, the signal representative of the event continues for a delay 210, operational part 115 transmits a message to agent 110, as illustrated in the second and third lines of FIG. 2. If the signal continuing during delay 210 does not continue during consolidation delay 215, agent 110 does not transmit a fault diagnosis message to CMS 120, as illustrated in the second line of FIG. 2. If the signal that has been continued during delay 210 also continues during consolidation delay 215, agent 110 transmits a fault diagnosis message to CMS 120, as illustrated in the third line of FIG. 2.
It is important that the detection results are consolidated in time by the agent, in order to avoid mistaking transient events for events representing a fault.
In addition, it is important that detections of faults are stamped with a time as close as possible to the real fault instant, in order that the algorithms of the CMS 120 will correctly correlate the messages.
In certain systems, by virtue of empirical sets of rules, the confirmation times must be readjusted. The new value for the confirmation time is sometimes obtained from ground tests (on a bench) or even flight tests. These readjustments take place too late in the development and sometimes even after the airplane has been placed in service, thus increasing the development costs and the maintenance costs due to unjustified replacements of equipment items and to the time lost on the ground for fault-finding.